I was reading through comments on a YouTube video on a late model Victa 2 stroke mower and some were saying they use 50:1 instead of 25:1 as long as it's semi synthetic, full synthetic or good quality oil.
A Lawn Boy 2 stroke owner in America claimed he was using much leaner mixtures with his 16:1 specified mower for years without problems.

Is it a risk of overheating or engine damage in harsh mowing environments?

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!